iskorotkov/avro: CPU Exhaustion in Decoder

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-46385: 0.61% estimated exploitation activity in the next 30 days; percentile 49.47 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

CPU Exhaustion in Avro Decoder via Unbounded Block-Count Iteration Summary The Avro array and map decoders looped over an attacker-controlled block-count value without checking the underlying reader's error state inside the loop body. Reader.ReadBlockHeader returns the count as a Go int, which is 64-bit on amd64 / arm64 targets — so a producer can declare a block of up to math.MaxInt64 (~9.2 × 10¹⁸) elements followed by EOF (or any truncated payload), and the decoder will attempt that many no-op iterations before propagating the error. The realistic ceiling is "indefinite until the worker is killed externally" — a single hostile payload pins a CPU core until the process is OOM-killed, deadline-cancelled, or terminated. Remote, unauthenticated denial-of-service. The fix exits the loop on the first inner-decode error. It does not bound the loop length itself; for full coverage on untrusted inputs, also configure Config.MaxSliceAllocSize and Config.MaxMapAllocSize (the latter introduced…

Published by the source

27 Jul 2026, 16:16 UTC

Last modified by the source

5 Aug 2026, 03:41 UTC

Source last checked

26 Oct 2026, 15:23 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w8j3-pq8g-8m7w

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GO-2026-5046

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# Patch Next advisory brief: CVE-2026-46385

Advisory: iskorotkov/avro: CPU Exhaustion in Decoder
IDs: CVE-2026-46385, GHSA-w8j3-pq8g-8m7w
Record: https://patchnext.com/advisories/cve-2026-46385 (revision 3, source checked 26 Oct 2026, 15:23 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/iskorotkov/avro/v2 2.33.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/hamba/avro/v2: affected every version
- Go github.com/iskorotkov/avro/v2: affected < 2.33.0; fixed in 2.33.0

## Suggested inspection (read-only)
- Go github.com/hamba/avro/v2: check the installed version with your package manager.
- Go github.com/iskorotkov/avro/v2: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/hamba/avro/v2, github.com/iskorotkov/avro/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-5046 (OSV record GO-2026-5046 lists affected ranges: Go github.com/iskorotkov/avro/v2 >=0 =0)
- Verified: https://github.com/advisories/GHSA-w8j3-pq8g-8m7w (GitHub-reviewed advisory GHSA-w8j3-pq8g-8m7w lists affected ranges: Go github.com/iskorotkov/avro/v2 >=0 <2.33.0)

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